A Novel Synchronous Signal Detection Method without Phase-Locked Loop Based on EEMD

In order to achieve more efficient control of three-phase grid-connected converters., it is particularly important to extract the positive-sequence fundamental frequency signal of the power grid quickly and accurately. However, the detection performance of the traditional Phase-Locked Loop (PLL) technology is difficult to achieve the expected effect under the condition that the three-phase grid voltage contains a Direct-Current (DC) component, an asymmetrical fault, and severe distortion. Considering of the above problems, the paper proposes a novel synchronous signal detection method without Phase-Locked Loop based on EEMD (the empirical mode decomposition theory and the overall average empirical mode decomposition) algorithm. The method uses EEMD to decompose the input voltage signal into a finite number of intrinsic mode functions (IMF), and then extracts the positive-sequence fundamental frequency component by the maximum correlation coefficient method. Theory and simulation show that the proposed method can accurately collect the voltage synchronization information of the grid under the conditions of unbalanced three-phase voltage, abrupt phase frequency change, harmonic and DC components.